1. Field of the Invention
The present invention relates to a high-temperature stable alumina that does not transform into .alpha.-alumina even at a high temperature equal to or greater than 1300.degree. C., in particular, a high temperature exceeding 1400.degree. C., and a method for manufacturing the same. The high-temperature stable alumina of the present invention does not undergo a sharp reduction in specific surface area even at high temperatures, and is useful as a carrier of an automotive exhaust gas cleaning catalyst.
2. Description of the Related Art
Alpha (.alpha.)-alumina, which is a high-temperature stable phase of alumina, is widely used due to its excellent characteristics as an industrial material. Various transition-type aluminas obtained by, for example, dehydration of alumina hydrates, are normally porous and have great specific surface areas. Therefore, the transition-type aluminas are excellent in absorption power, catalysis power and the like, and widely used as desiccants, catalysts, catalyst carriers and the like.
However, a normal transition-type alumina starts to transform into the phase of .alpha.-alumina at a temperature of about 1000-1100.degree. C. and, simultaneously, starts to undergo rapid particle growth, resulting in a considerable reduction in specific surface area and, therefore, deterioration of the functions as a catalyst or a catalyst carrier. This has become a big problem in applications as, for example, a carrier of an automotive exhaust gas cleaning catalyst, which is frequently exposed to high temperatures.